Three major analog television standards are NTSC, PAL, and SECAM. The National Television System Committee developed the NTSC standard in the U.S. in 1953. NTSC is used in United States, Canada, Japan, in most of the American continent countries, and in various Asian countries. NTSC runs on 525 lines/frame with a vertical frequency of 60 Hz and a framerate of 29.97 frames/sec.
The PAL (Phase Alternating Line) standard was introduced in the early 1960's in Europe. It has better resolution than NTSC, with 625 lines/frame. The framerate is slightly lower than that of NTSC, being 25 frames/sec. PAL is used in most western European countries (except France), Australia, some countries of Africa, some countries of South America, and in some Asian countries.
The SECAM (Sequential Color with Memory) standard was introduced in the early 1960's. SECAM uses the same bandwidth as PAL but transmits the color information sequentially. SECAM runs on 625 lines/frame with a framerate of 25 fps. SECAM is used in France, former French colonies, and in former communist countries in Europe.
Color can be created by selectively weighting combinations of a Red component, a Green component, and a Blue component (RGB). Analog video standards translate the RGB components into luminance (Y) and chrominance (C). Chrominance is a two-dimensional component. The PAL and SECAM standard use U and V to denote these two dimensions. The U signal is based on the difference between the Y component and the Blue component. The V signal is based on the difference between the Y component and the Red component.
The NTSC standard uses I and Q to denote the two dimensions of chrominance. The I-Q plane differs from the U-V plane by a 33-degree rotation and axis-swap. This rotation puts the I color axis in the orange region of the color space, which is where flesh tones are found. Since the human eye notices detail in the color region represented by the I component more easily than other those in the Q component, I can then be given a higher bandwidth than Q.
In standards such as NTSC, PAL and SECAM, the Y and C components are combined into one composite video signal. When the Y and C components in a composite analog video sequence are separated, the Y component may add interference to the C component. This is called cross-chroma interference. Similarly the C component may add cross-luma interference to the Y component. In the evaluation of the video sequence, the cross-chroma and cross-luma interference may be interpreted as motion, noise, or other artifacts. Various processing may be applied to the analog video. However, cross-chroma and cross-luma interference may lead to inaccurate noise characterization, especially during scenes with motion.
Limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.